Antiaircraft shell



C. A. WHITSETT ANTIAIRCRAFT SHELL June Z5, 1946.

` 8 Sheets-Sheet 1 Filed Oct. 18, 1940 June 25, 1946. c. A. wHrrsETT ANTIAIRCRAFT SHELL Filed Oct. 18, 1940 8 Sheets-Sheet 2 June 25, 1946. Q A, WHrrsET-r 2,402,716

ANTIAIRCRAFT SHELL Filed Oct. 18, 194() 8 Sheets-Sheet 5 we fu June 25, 1946. c. A, WHITSETT ANTIAIRGRAFT SHELL Filed oet. 18, 1940 8 Sheets-Sheet 4 June 25, 1946..

c. AgwHlTsE-rT 2,402,716

ANTIAIRCRAFT SHELL Filed 0G13. 18, 1940 8 Sheets-Sheet 5 June 25, 1946.

c. A. wHrrsETT 2,402,716 ANTIAIRCRAFT SHELL Filed Oct. 18, 1940 8 She'ets-Sheet 7 'June 25, 1946.

l I c. A. wHlTsETT 2,402,716

ANTIAIRGRAFT SHELL l Filed oct. 1S, 1940 8 Sheets-Sheet 8 l 269 L 25? I y l `25? l l I l! i 255 I; 255

l l l \253 255 gw/ /a,

` INVENTOR. f Cameron, d?. W/usezz" I Patented June 25, 1946 UNITED STATE-s PATENr oFFlc-E f Y' 72,402,716 l Y ANTIAIRQRAFT 'SHELL' l Cameron A. Whitsett', Chicago, Ill.

Application October 18, 194i), Serial No. 3fi'1,761

The present invention; relates lto improvements in anti-aircraft shells and like devices lfor combating airplane attacks. In its preferred embodif ment, the invention is in the form of a projectile Y'i1 claims. (01.102-7-56) adapted to be red from antiaircraft guns Aof Y' the larger calibers, such as threeinch, '75 mm., 90 mm., and upward. However, as I shallhereinafter describe, certain features or adaptations of the invention may also be used in projectiles of smaller calibers and in other types of antiaircraft devices.

The shell as it is iired from the antiaircraft guns comprises a settable time fuse, a 'chargeof black powder or the like which serves, topat or open the shell at the altitude predetermined by the time fuse, a parachute which is released from the shell following the opening thereof3 and a reel of wire which is also released from the shell and which hangs down from the parachute j and suspends an explosive portion of the shell at its lower end. This concept Aof having anexplosive portion of the shell hanging from vthe lower end of the parachute wire, in the general nature of an aerial bomb or mine, constitutes one of the distinctive features of the invention. The wire in itself can inflict substantial damage against an aircraft running into it at high speeds, but the explosive shell carried by the wire greatly increases the destructive potentialities of the device against aircraft. In the preferred` embodiment of the invention, this explosive portion'of the shell is adapted to be firedby any direct contact with an aircraft, the charge preferably being a typical high explosive, such as TNT, which produces complete fragmentation of the shell and a high pressure wave. The high explosive charge is fired by a novel trigger mechanism whichis tripped by an endwise or sidewise contact with an airplane. The steel wire extending downwardly from the parachute to the explosive shell wire while in Ya steep angle bombing dive. Because `the angle of such a dive is usually almost as steep as the vertical angle of the suspended wire, there is a relatively small shock of impact placed lupon the wire by the wing or fuselage of the airplane striking itjthe relatively small'horizontal component of the planes motion pushing the wire ahead of it, and the relatively large plane. Y, Should any whip action occur in the lower vertical component of the planesmotion vir-Y tually running downithelength Yof the wire toward the explosive shell, solthat the wire guides the Shell into direct iiring contact with the airportion of the wire as the planenears the shell,

this will only ,throw the shell more forcibly againstthe plane.

fIn the vcase ofa horizontally ilying airplane striking the vertical wire, the shock ofrimpact against the. wireY and the resulting jerk on the parachute and on the' explosive shell will be considerably greater than in the. case of a diving plane striking the wire. However, my improved construction embodies shock absorbing featuresy which yield under these higher'stresses and avoid may be several hundred feet long,` and it is the Y of the wingrstructure, which projections would shell can effect very destructive damage on practically any size or type of airplane.

The defensive value of my improved parachute shell can be best illustrated in the case of a dive bomber striking the long span of intervening breakagerof the wire or disruption of the parachute. VWhen the leading edge of the airplane wing or fuselage strikes the wire, it jerks the intervening portion of the wire forwardly, .with the result that theparachute and `shel1I swing vertically ytoward each other, in rear of theV airplane, sothat the parachute, the wire, andthe shell are dragged forwardly in the form of a V-shaped horizontal loop. After the initial shock kof impact has been absorbed, Aand the parachute and explosive shellhave taken on therapproximate Vvelocity of the airplane, the .parachute will begin to exert a Vgreater drag on its end of the steel wire than the shell does on the' other end Y of the Wire, with the result that the parachute `will have a relative dragging motion to the rear,

thereby drawing the shell forwardly and into firing contact with the plane.

. The average bombing plane, pursuit plane, or other combat plane usually has various projections extending forwardly from the leading edge serve very eiectively to prevent the span of ,steel wire froml slipping laterally olf the tip end of the wing. For example, machine guns built into Vthenwing structure usually havetheir barreis Vprojectilflg forwardlyV in such positionthat they would serve as projections for limiting outwardrmovement of the wire, and the samezwould also be trueV of pitot tubes' and the like projecting forwardly from the Wing structure'for consuch grappling hooks and wires is to establish a hooked engagement against the trailing edge of the wing Istructure or other adjacent part of the airplane so as to prevent the main span of wire 'from sliding outwardly along the wing structure toward the tip end of the wing, this being hereinafter described more in detail.

The parachute is made as invisible as possible to enemy aircraft, either by constructing it of a very translucent material, or by coloring it with a very inconspicuous or camouiiaging color. The steel wire need only be of very small gauge and is hence invisible only a few feet away, and the explosive shell is relatively small. Consequently, to a plane traveling 200 or 300 miles per hour, the parachute shell would be extremely diilcult to see before being actually struck by the plane. The possibility of a plane shooting down these parachute shells with machine gun nre would be extremely remote because of the relatively small size of the parachutes, and the fact that a few bullet holes would not seriously impair them.

Another feature of the invention resides in providing improved safety means in the shell for i preventing the detonation thereof when the shell strikes the ground. This safety feature greatly reduces the damage done to dwellings, personnel, etc., by shells which drift to the ground in populated areas. Still further, this safety feature renders a large proportion of the 'shells which settle to the ground recoverable so that the shell can be recharged and the parachute reclaimed for future use. Hence, the cost of a large scale aerial barrage based on the use of these parachute shells is greatly reduced because of the large proportion of recoveries of unexploded shells.

In a typical use of my improved antiaircraft projectiles, a large barrage oi them might be periodically or continuously red in a predetermined pattern or grouping from the antiaircraft guns so that the individual parachute shells descending therefrom would form in eiect an aerial curtain or barrier so positioned as to prevent enemy aircraft from getting within bombing range of a particular ground target. The antiaircraft projectiles can have their fuses timed to open and release the, parachutes at any altitude in the trajectory of the projectiles, as for example at altitudes as high as 20,000 to 30,000 feet or more. Owing to the relatively slow rate of descent of the parachutes, it will be evident that the shells which are opened at these high altitudes will require a substantial time to settle down to the ground, ranging anywhere from a quarter of an hour to a half hour or more, depending upon the altitude setting, the size of the parachute, etc. Hence, it will be seen that the defensive value of each shell continues for a substantial period of time throughout the entire range of altitudes at which a bombing attack might be made. Successive salvos of shell-s may be timed to open at different altitudes for extending or concentrating the vertical barrier formed by the parachute shells. One of the particular merits of this form of aircraft defense is that it enables the antiaircraft guns to go into immediate action upon any advance warning of an attack, and to establish a defensive barrier of parachute shells a considerable time before the enemy aircraft are even visible. Thus, the defensive value of antiaircraft guns is no longer confined to what may be a very short period-of peak re which is only eiective during the time that the enemy aircrait are actually visible; but, to the contrary, by the use of these parachute shells, the guns may be fired continuously at a maximum rate of fire to bring about an aerial mining of the 'sky either in advance of a raid or during a raid. The value of this form of defense is particularly Well illustrated in the case of night raids, er raids during cloudy weather, or at extremely high altitudes, when there isvery limited visibility for accurately aimed're of the antiaircraft guns. The latter are usually of the rapid iil'e type capable of liring 30 ory more shells per minute, from which it will be seen thateven ten minutes of intensive re from one Vof'these guns can establish a mined curtain or zone of 300 parachute shells or so. Such aerial mining of the sky over the ground target that is to be protected may be carried on in advance of a forewarned bombing assault until such time as theenerny aircraft have become visible or are within range,V whereupon the strategy of fire of some or al1 of the guns may be changed so as to fire timed high explosive shells in accordance with present day practice.

Other features, advantages, and objects of the invention will appear frornthe following detailed description of certain preferred embodiments thereof. In the accompanying drawings illustrating such embodiments:

Figure l is a longitudinal sectional View through the shell, showing the condition that the shell is in at the time that it is'loaded into the antiaircraft gun;

Figure 2 is a fragmentary longitudinal section on a larger scale, showing the front and rear sections of the shell in the act of being parted, preparatory to releasing the wire and the parachute;

Figure 3 is a detail sectlonal View showing the 50 I ring plunger in its forward position in the act of ring the primer, as a result of the front shell section having been brought into iiring contact with an airplane;

Figure 4 is a similar View showing the primer shifted down into its safety position, into which it moves when the parachute shell has drifted down and has struck the ground;

Figures 5 and 6 are sectional views taken on the planes of the lines 5-5 and 6-6 of Figure 2;

Figures 7 and 8 are sectional views taken on the planes of the lines 1-1 and 8 8 of Figure l;

Figures 9 and 10 are fragmentary sectional views taken on the planes of the lines 9-9 and lil---Ill of Figure 2;

Figure 11 is a fragmentary sectional view showing the front shell section suspended at the end of the parachute wire, with its trigger mechanism in cocked positionA ready to be red by contact with an airplane;

Figure 12 is a detail sectional view of a modied construction corresponding to a section taken on the plane of the line l2-i2 of Figure 2;

Figure 13 is a fragmentary sectional view showing a modied operating arrangement between VtheV clutch jngers and the ring plunger;

Figure 14 is a fragmentary sideview of the shell with a central portion broken away to illustrate one of the trigger assemblies in its folded position in the shell;

Figure 15 is an end View of the skirt or cage portion of the front piston section, different portions being shown on different sectionv planes;

Figure 16 is a fragmentary detail View ofthe end ring of the piston assembly;

Figure 17 is a similar view of another vportion of the piston assembly;

Figure 18 is a detail sectional view taken on the plane of the line |8| 8 of Figure 15;

Figure 19 schematically illustrates a dive bomber striking the intervening wire of the'parachute shell; f

Figure 20 shows the action of the parachute and wire in drawing the shell into firing engagement with the trailing edge of the airplane wing;

Figure 21 illustrates the shell in the act yof striking the underside of the airplane wing, which results in the firing of the shell by lateral contact against the trigger mechanism;

Figures 22 and 23 similarly show the action of the parachute and wire in drawing the shell into ring engagement with the wing or other portion of the aircraft in the case of an airplane flying substantially horizontally;

Figure 24 is a plan view of a modified construction of parachute having elastic upper gussets for yieldingly varying the size of the upper vent opening, so as to minimize shock stress in the parachute;

Figure 25 is a side view of another modified construction of parachute adapted to avoid vshock stress by slipping one side ofk thechute;

Figure 26 is a similar View of still another modified construction of parachute; Y

Figure 27 is a fragmentary side view of a modified arrangement in which the rear section of the shell remains suspended from the parachute wire after the opening of the shell;

Figure 28 is a fragmentary side View showing another modified arrangement in which grappling hooks and grappling wires are suspended from the parachute wire after the opening of the shell;

Figure 29 is a fragmentary plan View of an air plane wing showing the action of said grappling hooks in preventing the slipping olf the end of the wing;

Figure 30 is a detail view on a magnified scale showing the mounting and arrangement of such grappling wires on the parachute wire;

Figure 3l is a fragmentary perspective View showing a form of metallic tape which may be used as the suspension member instead of wire; and

Figures 32 and 33 show a modified construction in which the shell is convertible into a timed high explosive type, these views corresponding to asection taken on the plane of the line 32--32 of Figure 1.

Referring t0 Figure 1, the shell is designated 3| in its entirety, this gure illustrating the shell in the form in which .it is fired from the antiaircraft gun as a projectile. In typical antiaircraft ordnance, such a shell is the projectile of fixed-load ammunition, although it will be understood that the invention can also be embodied in the projectiles of loose loading ammunition. The main case of the shell comprises a front section 3Ia and a rear section 3io, these two sections being joined together at a separable joint 32. Said joint comprises an inner annular parachute wire ange 33 carried by the front section, andan outer annular flange 34 carried by the rearvsection, these. two flanges having a relatively tight push fit.A Anyv suitable type of shear fastening may be employed to secure the'two sections together, such as shear pins, a shear thread, or a shear wire, etc. In the exemplary construction illustrated, a shear wire 3fcomposedfofbrass, aluminum, or other readily shearable metal,V occupies the ring-like channel which is defined by the matching grooves 36 of semi-circular-cro'sssection' formed in the flanges 33 and 34. "The wire may be inserted into said matching grooves,

after theshell sections have been assembled-by introducing the wire throughV a Vtangential 'opening leading tov said grooves. Ther'ez'irsection` 3Ib carries the rotatingband 38, and-the `front section 31a is shown as being formed ywith the bourrelet`39, although the bourrelet might be formed on the rear section if the latter were of considerable-length. v Y 5 v Y P'aekedwithin the rear end of therear section 3| b is the parachute 4I', and disposed forwardly of the parachute is the reel or coil of steel'wire 4 2.` Confined within the forward section 31a is the charge ofY high explosive 43,'this forwardportion 'ofthe shell being the explosive portion which is suspended at the lower end ofthe steel V`,wire 42, alsA clearly illustrated in Figures 19 to 30 inclusive. Mounted at the forward end kof the front section 3m is the fuse 44 that gives the variable time delay that enables the shell lto be opened at any desired altitude within the range of its trajectory. The fuse shown is acompound or combination fuse structureperforminga'f'pluralityy of fuse-functions.V

there is also the detonating functionV `ofgiirjing the' charge of high explosive 43 -whenthe'tri'gg'er mechanism of the cocked shell `hasstruckfagainst an airplane. I have also shownthe fuseystruc-A tureV as performing 'the third'function lof a percussion fuse which Vservesto fire the'charge'jof high explosive 43 inthe event of percussion contact of the shell against any part of an airplane structure while the shell is travelling through the upward part of its trajectory, before opening.

The opening of the shell is performed by the firing of an opening or parting charge of black.

powder or the like 4l which is confined within a chamber 48 formed in the rear end of the'front shell section .'3Ia. rlfhe kfiring of this opening charge acts against a` piston 49 which denes the rear wall of the chamberldhwhereby said piston is forced rearwardly for parting the rear section of the shell from the front section. Such rearward h motion of the piston 49 also cocks the trigger plosive charge 43 is closed at its rear endfbythe transverse wall or diaphragm 54'.' AS shown in Figure 5, a` plurality of filling apertures vF55' are provided in this end wall, through which the high explosive'ispoured in the molten state inthe filling operation, these apertures'being thereafter closed bythe threaded plugs 56..Y The other end of the high explosive chamber 53 is closed by the fuse plugor fuse head `58, the'shank of whichV screws into a long internal. thread 59 formed in F For example., there) is Vthe time function of determining* thefjtinielor .f altitude) at which the shellis tobe opened; and

the outer end of the front shell section 31a. Extending rearwardly from this fuse plug 58 is an integral tubular stern 6| carrying a threaded closure portion 62 at its rear end, which closure portion screws into a rear internal thread 63 formed in the end wall 54. The front internal thread 59 and the rear internal thread 63 are of the same pitch and are preferably cut at the same time by different size threading hobs on the same cutting tool, so as to receive without binding the two threads on said fuse plug and on said closure portion. An optional method of introducing the high explosive charge 43 into the chamber-53 is to rst pour and solidify a filling of the explosive within the chamber through the threaded front end 59, then to drill out a central opening through the exposive or to mold a central opening therein during the pouring and solidifying thereof, thereafter to pass the stem 6i and threaded closure portion 62 through this opening and into assembled engagement within the front and rear threads, and nally to fill all remaining voids in the chamber 53 by supplementary pouring operations through the filling aperturesr 55.

YExtending longitudinally along the length of the tubular stem 6l is a raised rib B5 in which is cored a flashback passage 66 through which the ash of a detonator 61, disposed in the fuse plug 58, is conveyed back to the opening charge of black powder 41 disposed in rear of the partition wall 54. The flash-back passage 66 is clearly shown in Figure 4, and, as shown in Figure "I, the detonator, primer, or like firing charge 61, which may be composed of fulminate of mercury or other suitable type of detonating explosive, is

preferablyra pellet of arcuate form, packed into an arcuate cavity 63 cored out in the fuse plug 58'. Said cavity is open only at its front end, through which the detonating pellet is inserted, and said open end may be closed by any suitable gasket of paper or other'ignitable material. This detonator is adapted to be lired by the adjustable time fuse contained within the fuse structure 34, which time fuse has previously been set to open the shell at a predetermined altitude, as will be later described. Preferably, the passage 66 is left open so as to conduct the flash of the detonator 61 as an instantaneous flame discharge back to the charge of black powder e1, but, if desired, a powder train or other fuse medium may be extended through said passage for securing additional time delay, or for any other purpose. The charge 41 for opening or parting the shell is preferably black powder, but might be any other suitable explosive of a relatively slow burning characteristic. This opening charge 41 is preferably enclosed within a thin igntable container 69 composed of paper, cardboard, fabric, etc., which prevents any frictional contact of the charge with surrounding metal parts under the set-back force which occurs in the firing of the projectile from the gun.

Referring again to the transverse sectional View through the fuse plug 53, Figure '1, the remaining portion of the plug not occupied by the detonator cavity 68 is formed with a second relatively long arcuate cavity 1| in which is enclosed a booster charge 12, also preferably in the form of an arcuate pellet, composed of tetryl or other suitable booster explosive. This booster pellet is packed into the open rear end of the latter cavity 1 I, and is retained therein by a thin sheet metal gasket or cover 13 pressed into the cavity. This booster charge is provided for the purpose of igniting the high explosive charge 43, the booster charge blowing the cap 13 rearwardly from the open rear end of the cavity 1|. Said booster charge is lired through a passageway 14 by a primer 15 which is disposed substantially centrally within the fuse structure 44, this primer being red as the rst step in the bursting charge train, through the impingement action of a Semple centrifugal plunger 16 or other suitable firing mechanism, as I shall presently describe. Formed as an integral extension of the fuse plug 58 is a forwardly projecting central sleeve 8l which has an internal thread 32 at its front end. Screwing into said thread is a companion thread formed on an inner sleeve 84 which projects iorwardly from the outer sleeve. Said inner sleeve has its outer end formed with a spider structure or apertured head portion terminating in a forwardly extending central boss 86. A sernspherical end cap 83 screws over a thread on this boss 86. A plurality of venting passages B9 are cored out in the end cap 88, these venting passages communicating with other venting passages 9i extending through the aforementioned spider structure and opening into the chambered interior of the inner sleeve 84. These venting passages may be utilized for interior venting of the time-train rings S2 and 93, and may also be utilized for venting the primer 15 if the latter should become accidentally red upon striking the ground after the primer has been moved forwardly to its safety or non-firing position,

Slidably mounted in a cylindrical bore formed coextensively in the thread boss 86 and end cap 83 is a conventional concussion plunger 56 which is normally held in the forward position shown in Figure l by the friction ring 91 engaging in the grooved exterior of the plunger, this being a well kown construction in powder-train time fuses. The set-back force which occurs when the shell is fired from the gun frees the plunger from the friction ring, and the resultant inertia eifect carries the plunger against the concussion firing pin S8, as shown in Figure 2, so that the concussion primer in the plunger is fired. The flash from this primer is conducted laterally through a passage 99 which extends through one arm of the spider structure and opens into the annular powder channel of the outer time-train ring 92. The powder in this channel burns around to a point where it meets a port which is formed in the front surface of the next timetrain ring 93, which port conducts the delayed combustion into the annular powder channel of this next time-train ring 93. The latter ring is rotatable to different angular positions relatively to the front ring 92, thereby increasing or decreasing the total length of the powder train in the two rings and hence varying the altitude adjustment at which the shell is set to be opened for parachute descent. The structure and operation of such powder-train time fuses are old and well known and need not be described in any greater detail, reference being had to pages 589-592 of Elements of Ordnance, by Hayes,

Y for complete disclosure of one typical construction which may be employed. This construction may be such that the combustion in the second time-train ring 93 will be conducted from one angular point in its powder channel directly to the detcnator 61 which fires the opening charge of black powder 41, as previously described. illustrative of an alternative construction, also propose adding a stationary spacer ring m2 and a third rotatable ring I3. The spacer ring |62 is held against rotation by a kerf or key 1M (Figure 10) projecting inwardly therefrom and'seating in a keyway I formed longitudinally in the outer end of the sleeve 8|. A single port |03 in this stationary ring establishes communication between the second and third powder train rings 93 and 03. The powder channel in said third ring transmits the firing propagation into the detonator S1. This occurs through a rearwardly facing port |08 in said third ring which .can be turned into and out of registration withv the detonator by rotating said third ring. As shown at the lower side of Figure 2, said third ring also carries a right angle port I 09 which is adapted to establish right angle communication between the primer 15 and the passageway 14 leading to the booster charge 12. It will be seen from the foregoing that this third ring |03 can be utilized as a safety ring, since by rotating this ring to a safety position the port |08 can be turned out of registry with the detonator 61, and the right angle port |09 can be turned out of registry with the booster charge 12, thereby increasing the safety factor of the shell during storage and handling. This third ring |03 would be rotated back to its firing position at the same time that the second ring 93 is rotated to the set position which predetermines the altitude at which the shell is to open. Said third ring is also adaptable to other utilities, such as for increasing the total length of powder train in order to give a greater time delay for higher altitudes, and as a still further utility to enable the shell to be converted into a timed high explosive shell in which the high explosive charge 43 can be exploded at different adjusted altitudes by direct detonation from the powder ring time train through the booster charge 12, without releasing the parachute Il I. This will be described later. The three powder train rings 92, 93 and |03 can all be Vented exteriorly, or can all be vented interiorly through passages 89 and 9|, or two rings can be vented one way and the other ring the other way.

The primer 15 which lires the booster 12 and high explosive d3 is contained within a slidable metallic thimble II5 which is provided with a radial stop flange I I6 at its front end and a radial stop flange H1 at its rear end. The cylindrical body of the thimble has a snug sliding fit within a ring II 8 which' is pinned or otherwise secured within the end of the sleeve 84. The abutment of the front radial flange IIB against the front end of the ring denes the limit of rearward movement of the thimble (Figures 1 and 2), and the abutment of the rear radial flange II1 against the rear ends of the ring I I8 and sleeve 84 derlnes the limit of forward movement of the thimble (Figure 4). The thimble is prevented from rotating in said ring by the provision of a spline ||9 in the ring engaging in a groove in the thimble (Figure l0), or by any other suitable keying arrangement. The purpose of having the primer thimble shiftable between rear and front positions has to do with rendering the parachute shell non-explosive when the shell h'as drifted down to the ground and the nose of the shell has struck the ground. This takes the weight of the shell off the length of steel wire and permits the primer thimble to jump forwardly or downwardly to its safety position (Figure 4) as I shall presently describe. When the primer thimble is in its rearward or upward firing position (Figures 1 and 2) the thimble chamber is in position to fire laterally through a plurality of radially extending ports I2I (Figure 3) which register with stationary ports I 22. These stationary ports |22 in the ring .Seid Sprieg bears against a which is secured in the rear end of the springsus- II 8 and sleeve 84 open into the right angle-port or ports |09 formed in the third powder ring |03,Y leading to the booster charge 12. When the thimble is shifted forwardly to its safety position (Figure 4), the thimble ports are carried out of registry with said stationary ports and into registry Y with" the chambered interior of the sleeve 84,- forwardly of the ring H8. It will be noted'from Figure l0 that the front stop flange I It has scallops or apertures |24 therein which establish venting communication forwardly to the venting passages 89, 9|. Hence, if the percussion plunger 13 should re the primer 15 after the primer thimble has shifted forwardly or downwardly to the safety position it assumes as soon as the nose of the shell touches thergroundsuch ring'of the primer will be vented out through the front Vents 89 and 9 I, with very little likelihood of the booster charge 'I2 being fired. This-means that a large percentage of the parachute shells drifting to the ground will be prevented from exploding upon contact with the groundpr buildings, etc., and these shells can be recovered` and recharged for future use. g

A shifter spring |26 is kconfined under compression within a cylindrical bore I 21 in the fuse plug and bears against the rear radial langei Il of the primer thimble, tending Yconstantly to shiftY the primer thimble to its forward safety position. Acting in oppositionto said shifter spring are a plurality of angularly spaced rodsl 28, preferably four-in number (Figures 7v and 8), which have their front ends anchored in the primer thimble so that they can hold thefthimble drawnwback in its ring DOsition. These rods pass freely through guide openingsY I 29 extending entirely through the percussion plunger 16, said rods having-their rear ends secured to a disc or head I3I .whichis fastened to the front end of a long spring suspension sleeve |32. Conned within said sleeve is a very long cushioning spring |33, whichwaifords a spring cushioned suspension of the explosive portion ofthe shell at the lower end of the steel wireVA 42 during `the parachute descent` Said spring'surroundsa plunger rod |34 which carries `a piston head |35 at its forwardy end against-which the vcushioning spring-bears. The other end of guide vbushing` |36 pension'sleeve- |32, and .through which bushing the spring rod I34. is guided." The outer'end of said rod isprovided with a head I 31 lto which the lower end of the steel suspension Vwire 42 is anr` chored. The aforementioned shifter, spring I 26 hasfa compression pressure which is less than the weight of the explosive portion Sla of the shell, and hence when this portion of the shell is hanging suspended, from the parachute the weight of the shell is transmitted through'V the cushioning spring |33, sleeve |32 and rods |28 to the primer thimble IIE, for holding the thimble in its retracted firing position against thepres sure of said shifter spring |26. However, when the nose of the'shell strikes the ground Kor vother supporting surface in the parachutendescent'of the shell, the weight of the shell isrtakren oiV the spring suspension sleeve |32so that the shifter springk .|26 can shiftth'e sleeve |32, rods |28 and primer thimble II5 forwardly for placing 'the primer thimble inV its safety position (Figure 4). The long cushioning spring |33 is preferably relae tively *stiff so that the weight of therexplosive, portion ofthe shell.only compressessaid spring V a relatively small amount duringparachute descent. One of Vthe primary objects of said cushioning spring is to cushion the shock load'placed upon the wire when a horizontally flying airplane strikes the wire, and to this end the cushioning spring has a very long range of relatively hlgh deflection pressure for absorbing impact shock. In the condition in which the shell leaves the muzzle of the antiaircraft gun, the primer thimble is held back in the firing position shown in Figure l by a releasable split Wire ring |33 which engages in an annular groove |39 formed in the forward portion of the spring suspension sleeve |32. This locking ring locks said sleeve and primer thirnble in the forward positions shown until the shell is opened for parachute descent, as I shall later describe.

Referring now to the percussion plunger 15, this device is slidable along the rods |28 and 1s provided with an outwardly extending flange |42 having guided movement within the relatively large cylindrical bore |21. The shifter spring |25V has its rear end bearing against said flange, and thereby tends to hold the plunger in its rearward position, with the flange |42 abutting against the rear end of the large bore |21. Extending rearwardly through the stem 6| from said large bore is a smaller bore |44 which continues throughout the length of the stem. A sleeve ex tension |45 is formed integral with or is secured to the plunger 16 and extends rearwardly a short distance within the bore |44. When any of the trigger mechanisms 5| strikes an airplane and is tripped, a forward firing impetus is imparted to said sleeve extension for carrying the plunger 16 forwardly into firing engagement with the primer 15, as I shall hereinafter described.

The percussion plunger preferably contains a safety type of firing pin mechanism which will make the projectile bore-safe, i. e., prevent the firing pin moving into effective position until after the projectile has left the bore of the gun. The Semple type of firing pin responsive both to centrifugal force and inertia is representative of one form of bore-safe firing pin which may be employed, although other constructions may be used instead. The details of this Semple construction are known in the field of ordnance (see pages 519, 580, 581, and 590 of Elements of Ordnance, supra), and accordingly it is not necessary to describe it in all detail here. Briefly, the firing pin 16 projects from a weighted segment |41 which is arranged to swing in a longitudinal slot |48 in the plunger around a transverse pivot pin |49 (see Figures 7 and 8). Normally, the segment is positively locked in the position shown in Figure 1, with the firing pin inclined at a noneifective angle, through the locking function of centrifugally responsive plungers |5| which are slidably mounted in aligned transverse bores intersecting the longitudinal slot |48. Compression springs |53 thrust inwardly against said locking plungers, these springs preferably extending into hollow interiors of said plungers. The plungers normally extend into a locking opening |55 formed in the segment |41, both plungers abutting against each other midway of the depth of said locking opening. In such position of the plungers, the segment |41 is positively locked against swinging movement around pivot pin |49. In the firing of the projectile from the anti-aircraft gun, the high rotative speed imparted by the rifling sets up a substantial centrifugal force in the shell, which impels the locking plunger |51 outwardly so that the segment |741, is free to pivot forwardly around the pin |49. The weight of the segment is so disposed with reference to the fulcrum pin |49 that centrifugal force will tend to turn it about said pin and :arm the device by placing the flring pin 16 in a forwardly extending position. However, if there is considerable longitudinal acceleration of the projectile, which is the condition until it leaves the muzzle of the gun, the disposition of weight of the segment and firing pin with respect to the pivot pin |49 are such as to cause a turning effect opposite to and greater than that caused by centrifugal force. This feature prevents the ring pin from arming until after the projectile has left the gun, such armed position being illustrated in Figure 2, The firing pin now being armed, the shifter spring prevents the firing plunger moving forwardly by creep force while the projectile is in night.

By virtue of the above arrangement of primer thimble and percussion plunger, the shell is armed for direct percussion or graze nre practically as soon as the shell has left the muzzle of the gun. That is to say, if any of the shells being fired upwardly in barrage fire or otherwise should strike an airplane, the sudden deceleration or inertia shock on the shell will cary the firing plunger 16 forwardly into firing engagement against the primer 15, thereby igniting the booster charge 12 and exploding the high explosive charge 43. This percussion detonation will occur even if the shell should strike only a relatively frail part of the aircraft, since the plunger 16 is relatively sensitive to percussion inertia. In such percussion shock, the primer thimble ||5 cannot move forwardly out of its firing position because of the locking retention exerted by the locking ring |38 engaging in the groove |39 in the rearward portion of the sleeve |32. This locking ring is not forced out of said groove until the shell is opened for parachute descent.

Referring now to the arrangement whereby the tripping of the trigger mechanisms imparts firing impetus to the firing plunger 16, it will be noted that the shell-opening piston 49 has a threaded mounting |58 on a long guide sleeve 159 which has a free sliding fit over the spring suspension sleeve |32, Surrounding said guide sleeve, within the rear half of the cylindrical bore |44, is a heavy compression spring which is shown as being coiled of circular wire stock but which might be coiled of flat bar or ribbon stock for greater stiffness, if desired, The rear end of said spring abuts against a threaded bushing 152 which screws into the rear end of the bore |44, the sleeve |59 being guided in said bushing. rihe front end of said spring bears against a shiftable ring |53 which is free to run back and forth in the bore |44. The spring ll is preloaded with a substantial pressure, and this is borne at the front end by the slidable ring |63 bearing against a stationary stop ring |65 which is rigidly anchored within the bore |44, as by the radial pins |65 or in any other suitable manner. It will be observed that this stop ring is of small radial thickness, so as to leave substantial clearance between the inner periphery of the stop ring and the outer periphery of the sleeve |59. A shouldered end head |51 secured fast to the end of the sleeve |59 is sufficiently thin so as to be capable of moving rearwardly through said clearance space and picking up the shiftable ring |63. Hence, in the operation of parting or opening the shell by the firing of the parting charge of black powder 41, the rearward movementof the piston 49 and sleeve |59 will pick up the preloaded compression spring ISI and compress this spring to a substantially greater pressure. as

shown in Figure 2, Said spring may be so pro portioned that the condition of the spring becoming solid constitutes the end stop which determines the rearward limit of movement of the piston 49 and sleeve |59, or the engagement of the spring fingers |1| against the rear ends |1213 ofthe slots |12 may function as such, as described below. As the piston and sleeve approach the limit of this rearward movement, a pli rality of spring fingers I 1| moving therewith snap outwardly into openings |12 which are formed in the rear portion of the sleeve extension |45 projecting rearwardly from the firing plunger 16. These spring fingers function to establish a clutched engagement between the sleeve |59 and the sleeve extension |45, said clutched engagement preferably permitting a limited amount of endwise lost motion between the two. The fingers are preferably formed integral with or are secured to the shouldered end head |61 which is secured fast to the sleeve |59, being of resilient construction and so biased that they tend constantly to spring outwardly. Said spring fingers have shouldered ends |1|l which are capable of effecting a positive engagementI against the right angle shoulders |1.2a and |12b at the front and rear ends of the slots |12. To insure that at least one or more fingers will engage in one or more slots, there may be an even number of one and an odd number of the other, or, as shown in Figure 12, the clutch ngers may be guided endwise between pairs of longitudinal guide ribs |13 projecting outwardly from the sleeve |32. Normally, the shouldered ends of the fingers ride on the solid forward portion of the sleeve extension |45. As the shell opens for the ejection of the parachute, the shouldered ends of the ngers travel rearwardly and outwardly into the slots |12 and continue back to a position where they abut the rear ends |12b of said slots, or are in close proximity to these rear ends. This establishes a clutched relation between the sleeves |59 and |45 during the parachute descent of the shell, whereby the inertia shock set up in the shell by a high speed airplane striking the suspension wire 42 along a substantially horizontal flight path will not jar the sleeve |45 and per cussion plunger forwardly into firing engagement with the primer 15. However, when the suspension wire 42 guides the explosive portion of the shell into contact with the airplane, and the trigger mechanism is tripped by such contact, the quick forward motion of the sleeve |59 brings the clutch fingers up against the right angle front ends |12a of the slots, thereby picking up the sleeve |45 to travel therewith and driving the percussion plunger 18 home into firing engagement against the primer 15.

Referring now to the shell opening piston 49 and the trigger mechanism 5|, the piston assembly is of two-part or divided construction, comprising the front section 49a and the rear section 49h. When the opening charge of black powder 41 is fired, the two sections of the'piston start back together and continue their travel together until the rear section 3|b of the shell has been separated from the front; section 3|a and until the triggers 5| are free to fly outwardly to their cocked positions, whereupon the rear section 49h of the piston separates from the front section 49a and continues its rearward motion after the front section stops, such relative separation between the piston sections enabling the trigger linkages 5| to swing outwardly to their cocked positions (Figure 2).

14 The front piston-section 49a .comprisesa rel-A atively long cylindrical skirt portion |14which serves the dual purpose of a pusher element for separating the shell sections andV also vofa consecured against the front end of the cylindrical Y skirt member |14 by screws |19 (Figure 18)v which passv through openings in the ring and thread into tapped openings in the cylindrical member, thisring completing the outer peripheral portion of the front piston section 49a and having a moderately close sliding t withinrthe chamber 48. If desired, the inner periphery of this ring may be threaded for screwing over the external thread |16, 'or over a continuation of such thread, before being anchored `by the screws |19. In the parting of the shell, the separating forceexerted by the piston is transmitted rearwardly through the cylindrical cage or skirt portion |14 against an abutment ring |8| which has threaded'anchorage at |82 within the rear section 3 |b of the shell. This separating force shears the relatively soft shear vring 35, as shown in Figure 2, and then completely separates the two sections at the joint 32, following which the rear section of theshell' drops back quite rapidly because of its increased air resistance. Final venting of the remaining force ofv the black .powder preferably loccurs through a series of vent holes |84 which are formed'in the inner` flange 33, these being uncovered by the outer flange 34 and by the Vpiston 49 in the rearward movement vof said latter members. If desired, the stroke of the piston may be increased, or the parts othrewise proportioned, j'

so that venting will occur past the end ring |18 and outer edge of the flange 33. r

Referring now to the trigger devices 5|, these swing voutwardly from the skirt portionfof the piston as soon as the rear shell section 3|b has cleared the end of said skirt portion (Figure 2). As best shown in Figures 14-18, there is a series of these trigger devices grouped inv angularly spaced relation around the piston and said cage portion, eight of such trigger assemblies being shown although the series may consist of only six or any other number. Each trigger assembly comprises a central T-shaped link |81 and two side links |88 pivoted -together at |89 for outward and .inward folding motion. Each of these link assemblies folds inwardly into an individual rectangular recess |9| formed in the piston skirt |14 (Figure 15) so as to be received completely within said 'skirt portion. 'I'hese recesses extend entirely through the thickness of the skirt portion from end to end thereof; except that near the front end the under sides of the longitudinal bar portions |93 are formed integral with the threaded ring portion |15 (Figure 14). y n

The forward end of each T-shaped link |81 is formed with a pivot boss |95 which fits between two pivot lugs |96 projecting rearwardly from the end ring |18, a pivot pin |91 passing through said lugs and boss. By reason of the fact .that

theend ring and lugs constitute a separable unit, the T-shaped triggers |81 can all be pivoted thereto before assembly in the skirt portion. `The rear extremity of each T-shaped link is formed with laterally extending side bar portions so as to increase the area or span of the outer end of each link effective for contact against an airplane.

Coil springs |99 are arranged to act between each T-shaped link and its two side links |88, these springs being preferably coiled around the axes of the pivots |89 which join said links. The ends of said wire springs are hooked into notches or apertures in said links, and the bias of said springs tends constantly to swing the links outwardly, with each T-shaped link and its associated side links tending to open up or separate from each other around the axis of the knuckle pivot |89. Small pivot bosses may project laterally from the sides of the T-shaped lever |81 to space the side links |88 therefrom for accommodating said coil springs, or the pivot pins |89 themselves may provide lateral shoulders for spacing the side links.

The forward ends of said side links |88 have pivotal connection with the rear piston section Wb at the shiftable pivots 202, Said rear piston section is capable of sliding movement; toward and away from the front piston section 49a, being provided with a central guide boss or hub 203 which has a free sliding t on the spring suspension sleeve |32 (Figure 2). Projecting outwardly and rearwardly from this piston section at spaced points around its periphery are pairs of parallel bars 204. These bars rst extend outwardly a short distance and then extend rearwardly within the rectangular openings |9| in the cage portion |14. As best shown in Figure 14, each pair of parallel bars has close sliding fit along the parallel side walls of its associated rectangular opening. The pivot pins 202 pass through said parallel bars adjacent to the rear piston section 3|b, and then pass through the forward ends of said side links |80. These side links are adapted to fold down into the spaces which are dened between the parallel side bars and the central T-shaped link |31 (Figure 14). The rear ends of said pairs of parallel bars are secured to or formed integral with a continuous abutment ring 205 disposed immediately beyond the rear end of the cage or skirt portion |114` It will be seen from the foregoing that the rear piston section 49h, its central hub 203, pairs of parallel bars 204 and rear abutment ring 205 constitute a movable cage structure which is shiftable as a unit relatively to the front piston section 49a and its cage or skirt portion |14. The aggregate pressure of the multiplicity of coil springs |99 mounted on the several trigger assemblies 5| tends constantly to shift the rear piston section and its cage structure rearwardly by the action of urging the trigger assemblies outwardly to their cocked positions. The rearward limit of this relative shifting motion may be defined by stop links or like devices effective between the front and rear piston sections for limiting their relative separating movement. However, in the preferred construction illustrated in Figures 14, l5, and 18, the stop means is eiiective between the cage structures of the pistons, such comprising stop shoulders 201 carried by the front skirt or cage portion |14 engaging in longitudinal slots 208 formed in the pairs of parallel bars 204 of the rear cage portion. The stops 201 are in the form of studs projecting outwardly from radial side edges of Small attachment plates or clips 209 which are secured to the rear extremities of the longitudinal bar portions |93 by screws 2H threading into tapped- 16 holes in said bar portions. These stop plates 209 need only be mounted on a few of the longitudinal bar portions |93, the screws 2|| being inserted when the rear cage structure is shifted to its backward position as shown in dotted lines in Figure 14. The slots 208 in the parallel bars 2011 may be of any desired length for stopping the rearward movement of the shiftable pivots 202 at any desired point. This point determines the angular position which the side links |88 will assume relatively to the central levers |01 when the trigger assemblies are cocked. In this cocked position, the outer edges of the central levers have trigger contacts at the points 2 I3 against the inner edge of the flange 33, Said levers and links in this cocked position denne triangular struts which must be collapsed in the tripping of the triggers. The angle of inclination of the side links |88 is such that these triangular struts have just sufcient strength to resist the forward pull of the relatively heavy compression spring IBI acting through the sleeve |59. That is to say, a relatively small tripping force is adequate to collapse the triangular strut relation of the links and permit the links and piston to jump forwardly or downwardly under the impetus of the 'spring |6|, such motion carrying the clutch ngers |1| against the forward ends of the slots |12 and driving the ring plunger 16 into the primer 15 with resulting detonation of the high explosive 43. Referring to Figure 11, it will be clear that a relatively slight tripping force striking longitudinally against any point of the end ring 205 of shiftable rear cage 204, in the direction of the arrows X, will immediately collapse the strut relation of all of the links by carrying the shiftable pivots 202 downwardly, thereby permitting an instantaneous inward folding of all of the links. It will be noted that such direction of tripping blow is most likely to occur whenever the explosive portion 3|a of the shell is being dragged into nring contact with the airplane through the pull of the wire 42. Such direction of tripping blow is still effective even if it should miss the ring 295 but strike any one of the side links |88. The tripping of the trigger links will also result from the striking of a blow inwardly against the outer ends of any of the T-shaped links, as indicated by the arrow y in Figure 1l. This will exert a collapsing force tending to drive the rear piston section toward the front piston section, so that all of the trigger assemblies will collapse or fold inwardly simultaneously, with consequent forward motion of the firing plunger and detonation of the shell. Such direction of tripping blow is most likely to occur in any Whipping or sidewise swinging of the shell against a surface of the airplane.

In Figure ll, I have illustrated a modified construction in which trigger notches 2|3 of approximately right angle form are cut in the outer edges of the T-shaped levers |81 for engagin-g against the right angle inner edge of the flange 33. These trigger notches may be desirable for greater certainty of latching engagement against said flange, such as to reduce the likelihood of accidental firing in the case of descending parachute shells being blown sidewise against buildings or other vertical surfaces by relatively strong winds.

In this Figure 11, I have also illustrated a supplementary or alternative feature in the provision of a moderately heavy compression spring 2|5 which has its ends confined in cylindrical pockets 2|6 and 2|1 formed in the front and` rear piston sections. This spring tends to maintain the trigger links in their strut relation, and the pressure of said spring must be overcome in the tripping of said links for detonating the shell. Said compression spring may supplement the coil springs |99 mounted on the trigger links, or it may be employed in lieu of said coil springs, in which latter case the centirfugal force of the rotating shell may be relied upon to project the trigger links outwardly in the opening of the shell, or the shiftable pivots 202 may be located inwardly of a dead center line between the pivots |89 and |91 so as to exert an outward force on the links in the opening of the Shell.

It is opportune to remark at this point that in the preferred construction, the combined thickness of the two flanges 33 and 34 is depended upon to give the required strength at the separable joint 32 to withstand the set-back force which arises in the firing of the shell from the anti-aircraft gun, without regard to the relatively movable piston sections and their cage portions; but that, if desired, these piston sections and their cage portions might be arranged to sustain a, substantial part of the set-back force if it is desired to reduce the thickness of the flanges 33 and 34, for space considerations or otherwise. It will be understood that in the opening of the shell, the explosive force of the charge of black powder is transmitted through the solid portions |93 of the front cage and through the ring 205 of the rear cage into engagement against the abutment lvl-hg |8| which is screwed into the rear section of the shell.

Referring to the wire 42, this is preferably a drawn steel wire of extremely high tensile strength comparable to so-called piano wire, having a tensile strength of upwards of 300,000 pounds per square inch. Assuming the explosive portion 3 la of the shell to weigh in the neighborhood of 15 to 20 pounds, a drawn steel wire capable of sustaining a shock load of say ten times this weight, (1'. e., a load of 150 to 200 pounds) need only be approximately .0005 or .0006 of an inch in diameter. Assuming the shell which I have illustrated in the drawings to be of 90 mm. caliber and of conventional length, the size of the reel of wire shown therein would contain several hundred feet of such wire. By devoting more space to the wire or making a slightly longer shell, a length of a few thousand feet may be coiled therein, if desired.

The total amount of wire is preferably divided into two or more reel sections 42a, 42h, etc., so as to reduce the relative rate at which the wire unwinds r separates from any one part of the total supply, after the opening of the shell. For example, having the wire unwind from two reel sections results in an unwinding rate which is only half of the unwinding rate which would be necessary if the unwinding occurred solely from one reel section. This reduces the strain on the wire and on the parachute following the opening of the shell. The coils of wire are preferably impregnated or embedded in resin, Ipitch, rubber or other suitable material 2|8 which will offer substantial resistance to the unwinding of the wire from the reel sections. This material 2|8 is flowed in a molten or iiuid state into the interstices between the convolutions Vof wire in the winding of the reel sections, or immediately thereafter, so that when said material solidies it holds all of the turns of wire in an adherent mass, whereby the reel sections can be stored or assembled into the shells as substantially rigid 18 units. Furthermore, such material exerts a continuous retarding or braking effect on the unwinding of the wire, so as to slow down the velocity of the front section Sla of the shell as rapidly as possible, after the shell has been parted into its two'sentions. The quick slowing down of the front'shell section 31a reduces the shock which is imposed on the parachute 4| at the instant that, thev latter is withdrawn from the rear shell section and vfirst receives the full impact 'of the air stream, this quick reduction in velocity minimizingY the possibility of tearing or disrupting the parachute in lthe event that the shell is timed to openat a relatively low altitude where its normal velocity is very high. Instantly upon open-` ing of the shell, the rear shell section 3|.b decelerates at a more rapid rate than the front K shell section because of its greater air resistance and lesser mass, and in consequence the intervening span of wire starts tearing loose from the rear end of the front reel section 42a and from the front end of the'rear reel section 02h. Each of these reel sections is preferably secured in its respective shell section Sla and 3|b by an adhesive, or by a force lit, or in any otherY suitable manner; and if desired, they may be enclosed within cardboard or like containers loefore being secured in their respective shell sections. In Figure 2, the end walls 22| are illustrative of such containers or of cardboard spac-Y ers. The projection ofthe trigger assemblies 5| into their outward, cocked positions presents an area of very large wind resistance at the rear end ofthe front shell section 3|a, and this aids in rapidly decelerating said front shell section.

It may beV desirable to delay the ejection of the parachute 4| from the rear shell section 3|b to insure that the shell sections have been slowed down to velocities which will not tear or disrupt the parachute. This may be accomplished by making the rear reel section 42h function as a plug for retaining the parachute in place until substantially all of the wire of/said plug has been unwound. rTo this end, said wire plug,is wound to form an outer retainer flange which engages in back of the abutment ring |8I. In assembly,4 the parachute is packed in place and the wire plug 42h is then packed in front lof the chute, followingl which the abutment ring IBI is screwed in along the thread |82 to retain the chute and wire in place. According tothis arrangement, practicallyY all of the convolutions of wire must vbe pulled loose from the resin or other matrix material 2|8 in the plug 42h before the parachute can be drawn out of the rear shell section. Owing to the conical shape of said ywire plug, extending back into the front end of the packed chute,the unwinding of the plug leaves the front portion of the chute free to contract sufficiently to slip past the abutment ring |8|. In lieu of the above arrangement, the chute can be arranged for release or ejection almost immediately upon the opening of the shell, if desired. Of course, lthe front 4end of the wire in front reel section 42a is anchored to the head |31 on the outer end of the spring rod |34, and the rear end of the wire in rear reel section 42o is anchored to the shroud` lines of the parachute.

The invention embraces several instrumentalities to cushion the jerk or shock on the wire when struck by a high speed airplane traveling in a more or less horizontal flight path. Thelong range of yield of the spring rod'l34 constitutes one of these instrumentalities. Also, the fact that the steel wire 42 has remained in a tightly wound reel for a substantial time results in long spiral convolutions remaining in the wire even when suspending the front shell 'section from the para' chute, these long spirals affording a considerable range of elastic deflection inthe wire'.` 'In addition, the elasticity inherent in vseveral hundred feet of 'steel wire is considerable.4 As a still further instrumentality to absorb shock, I also con' template constructing the' parachute 4I so that there will be increased venting, slipping 'or spilling of *the air from the parachute until" the" shock or extremely high relative velocity'has 'been'absorbed.'4 Figure'24 shows a parachute having an eXpansible 'vent 23|' obtained by employing elastic upper' gussets 232 'which yield'under abnormally'high air pressures and increase the effective area of the vent 23!" in' the top' of the chute'. These gussets may be composed of rubberized fabric;v sheet rubber, 'or any other'thin, 'light elastic materi'al'suitable for such use'.' As the parachute starts slipping back'with reference to the forward m'otion of'the' plane, thereby' drawing the explo` sive' section of the shell'toward' the plane; the expansible'vent 23| diminishes in area Afor in' creasing the drag f the parachute. 'i

"'In'Figure' 25' 'I show another embodiment of parachutein which the shroudlines '235 at one side are "substantially non-elastic," while the shroud'lines'23'1 at't'he'other side, or over a lim'" ited segment of the parachute, are quite elastic' under high 'tensicn'stresses Hence', a sharp jerk or an" extremely high velocity 'imposed on the;

parachute'f'or a brief -interval will cause theA elas^ tic shroud' lines 231 'to yield or'p'ermitting one' side ofthe' chute 'to'spill the' air and reduce the" pressure," such being 'illustrated' by theA change from the dotted line position tothe full line position.' Th'eelasticity of the successive shroud lines 231 may he graduated to' result in' an even or gradua'tedsegment of the chuteperforrning this spilling function.' As the velocity of the parachute diminishes' this spilling ofthe air also diminishes, until thechute resumes its' normal shape.' Such spilling of the air from 'the' chute tends to cause it to travel sidewise, and at such times it is desirable'thatthis sidewisetravel be in4 a direction such' as 'to keep the" wire 42"drawn down""tight across the top of the airplane' wing. One expedient'fh'elpful in this regard is' to provide av Weight 239'o'r' to otherwise weight that side Aof' the parachutewhich has the non-elastic shroud lines' 235' so` that Vthis side will usually be lowe'rmost, and hence the 'sidewise slipping ofthe chute'w'ill be' in a downward direction.

In'Figure' 26 I have illustrated another construction'of'yieldable parachute in which there is provided' an inner set of non-elastic shroud lines-24l secured to an inner circular portion 243 of the chute, and an outerset of elastic shroud lines 225 secured to theouter edge of the chute. Ii' desired, the 'inner circular portion may be dei-'ined by a circular reenforcing cord 243 sewed or -woveninto the fabric, with the inner set of non-elastic shroud lines fastened to said cord. It Will be evident that an abnormally high air pressure can telescope the outer portion of the parachute, i. e. from the dotted line position to the full line position, but that the inner portion of the parachute will remain effective by virtue of'thenon-elastic shroud lines 24 l As the velocity diminishes the outer elastic shroud lines 245 keeppulling the outer portion of the chute for- Wardlyuntil 'iinally the chute resumes its normal shape, indicated in dotted lines. It will be evident that `each of the foregoing parachute constructions will readily yield and assume a condition of'reduced drag in response to' asharp jerk or a sudden high velocity, thereby minimizing the shock load stresses in `the parachutejwireand shell. As previously remarked, the parachute' is made as invisible as possible' to enemy aircraft; either by constructing it of, a very translucent material,or by'coloring it with a very inconspicu'- ous or camounagingcolor; 'For 'the purpose' of enabling ground observers to spot the parachute shells at high altitudes so as 'to calculate wind velocities and direction' of drift, s'ome ofjthe' para# chutes may lhave prominent'color bands, segments or other markings; and', ifl'desired these markings may be applied only 'to the undersurfaces of opaque parachutes so'as to be invisible to enemy planes from' the side or from above.A These marked parachute shells would bered only'at spaced time intervals for observing wind Velocities and the direction ofv drift at the altitudes Where the shells are expected to be most effective against enemy aircraft. vWith regard t'o` the area of each parachute, this may vary from approxi; mately 20 square 'feet to 50 square feet and upwards, depending upon the size of'the shell, the amount of space therein'V reserved forth@A 'para chute, etc. The length'ofwthe shell casing shown' is standard practice v'for timed high explosive shells of mm. caliber, but'where thel guns, caissons and other eouipment' permit theuse of a longer shell a greater volu'ne of the shell 'nay be devoted to the parachute. "Ifo'o large apara` chute may beundesira'ble' in some instancesj'because of the lng ydelayin the descending para-Y chute' shell reaching'the groundand'the 'consid'- erabie distance that such 'shells mignt'dnft in a high' wind.' These'drifting'` parachute shells` are potential hazards' "against'all' defense'planes as" Well as enemy planes'an'dit may "therefore be desirable that the par 'chute shells' descend tothe ground within a reasonabl'y'shorttime.vk

In Figure27 I have'illu'strateda modified arrangement in which the"rear^s'hell sectin'l b is not dropped to the ground upon the opening of the shell, but instead'is held'su'spended from the parachute wire 42'. In suchan arrangement, a separate suspension wire 241 has one end "anchored to the shellsection 3lb, andY has"its 'othei1r end'anchored at 249'tothe' parachute' wire" 42. rIfhis separate wire secured tothe'nterior of the sh'el1""se'ction, preferably at the inner end` thereofyand is then led around the outside of thev tained by 'this "general arrangement. First, there would be a much 'higher percentage of recovery of all parts of' the parachute shell for future use because'the` rear she'll"`s'ection vould A'always re'- main with' -the' 'parachute 'andwire even in'the casebf parachute'shells which' had been dtonat4 ed'by contact with airplanes, secondly, 'these reary shell"sectior'1s are' quite'h'eavy land 'a'large nurnber fof'thern 'falling in an intensive barrage might' do' substantial 'damage 'to buildings 'and ground"` personnel'. Furthermore, and possibly of greatest importance, the considerable weight or` mass of' this rear shell section mayr be utilized to balance' or'cmpensate the shock stress set up at the'other' end of/thesteel Wire by the relatively large mass of thefront shell section 31a. 'When an airplane strikesthe'wire 'with considerable shock; the par achute itself aiordsafvery small'ma'ss of inertia at the upper end of the wire, whereas the front shell section 3io. affords a 'considerable mass of inertia at the lower end of the wire. Hence, during this initial period of impact and high shock load there may be a tendency for the wire to run toward the shell section 3|a instead of toward the parachute 4|. However, by having the rear shell section 3|b remain suspended from the parachute wire, preferably at a point adjacent to the parachute, a substantial mass is made effective at the upper end of the wire for balancing a considerable part of the mass at the Alower end of the wire, whereby the parachute becomes effective more quickly for causing the Wire to run toward the parachute and draw the explosive section ala into firing contact with the airplane. In any entangling of the wire 42 in or around an airplane, the mass of this rear shell section 3|b also aids in establishing and maintaining such entangled relation.

Referring now to Figures 28, 29 and 30 which show a modified arrangement using grappling hooks and grappling wires so as to minimize the possibility of the parachute Wire 42 slipping laterally olf the end of an airplane wing, the grappling hooks 253 each consist of a plurality of grab hooks or prongs, preferably three or four in number, and radiating outwardly from a cluster, much in the manner of a gang type of shhook. The several prongs of such a grappling hook may be proportioned and arranged to fit over or across either or both reel sections 42a and 42??, or they may be of articulated construction so that they will fold into a very small space in the shell. This grappling hook is anchored to the lower end of a grapping wire 255 which is of approximately the same gauge or lighter than the parachute wire 42 and which is suitably wound with the parachute wire or disclosed between the reel sections thereof when assembled into the shell. Instead of a wire, this grappling strand 255 may be a twine cord or the like. Said grappling wire or cord does not need to be very'long; in the representative construction illustrated its length is approximately twice the chord of a typical airplane wing. The attachment of the grappling wire to the parachute wire is through a sliding friction tube 251. The grappling wire is xedly anchored to said tube, and the tube has a tightly engaging slide fit along the parachute wire 42. Instead of the tube 251, a tightly engaging slidable ring may be employed. Only one of said grappling hooks and wires may be provided, mounted on the parachute wire approximately midway of its length; or two or more of said grappling hooks and wires may be provided, spaced equal distances from each other and from the ends of the Wire or in any other desired relation. The theory of operation is that each grappling hook 253 will have a whipping action at the end of its grappling Wire or cord 255 so that if one of these grappling hooks is rapidly drawn up to the under side of the plane wing and around the front edge of the wing, under the action of the parachute jerking the upper run of the main suspension wire 42 backwardly, there will bea decided likelihood of the grappling hook 253 becoming caught over the trailing edge of. the wing structure, as shown in Figure 29. This trailing edge usually comprises ailerons, landing flaps and various other devices that form notches, projections or the like which would catch the grappling hook and prevent it from slipping outwardly toward the top of the wing. Thus, the grappling wire 255 and the guide 22Y l sleeve 251 would be prevented fromV sliding outwardly, even if lthe sweep-back `angle at the leading edgel of the wing tended to deflect the mainsuspensionv'rire 42 toward the tip of the wing'.` AAlthough the guide sleeve '251 would thus hold' the suspension wire from shifting outwardly, nevertheless the suspension wire could be drawn through the sleeve, and hence thel parachutev could pull the explosive shell section3|a up into ring contact vwith the airplane in the same manner as describedv before. If desired, av small stop bead 259 may be crimped or otherwise rigidly fastened to the suspension wire 42 to function as a limiting stop to be engaged by the upper end of the slidable guide sleeve 251, as clearly shown in Figure 30. This stop bead would prevent any possible reverse running of the suspension wire 42 toward the shell section 3 la after the grappling hook and' grappling, wire had snagged the trailing edge of Vthe wingfas by slipping across the top of the wing instead of across the under side thereof. If the main wire is equipped with two or more grappling hooks and grappling wires, there would still be only one stop bead and this would be secured to the suspension `wire at apoint above the uppermost guide sleeve 251. It will be understood that the stop ybead 259 isentirely optional, and that this is also true of the grappling hooks and grappling wire.

Figure 29 illustrates in dash and dot lines how any projection, notchor shoulder extending from the leading edge of the airplane wing or fuselage will serve to stop the suspension wire from sliding 01T the end of the wing. The projection m is intended to represent a wing type of machine gun.

While the suspension member 42 which suspends the shell section from the parachute is preferably a steel wire of circular cross-section, the invention is not limited to the use of this material or to this shape of suspension member. For example, it is conceivable that the suspension member might be in the form of a very thin ribbon or tapel 42t, as shown in Figure 31. This` would preferably` consist of other materials. The advantage of a tape over a circular wire would be thatY the iiat width of the tape would afford a bearing area of substantial width across the front edge of the airplane wing, so that there would be much less likelihood of the tape cutting into the front edge of the wing than in the case of a circular wire, This advantage would be predicated on the assumption that a free running suspension member 42 or 42t would be desired for drawing the shell section 3|a into firing c'ontact with the airplane, rather than a 'cutting member for cutting into the airplane wing. If grappling hooks are used in such embodiment, the guide sleeve or ring 251 is shaped like the metallic tape 4'2t. Y

In the embodiment shown in Figures 1 to 4 inclusive, th'e slots |12 in the sleeve extension |45 have/their rear ends formed as right angle shoulders 12b adapted toveffect a positively hooked engagement with the shouldered ends |1 I1' of the sprung fingers 1|, whereby the inertia shock set up in the shell by a high speed airplane striking thesuspension wire 42 along a substantial horizontal flight path cannot jar the sleeve |45 and percussion plunger 16 forwardly or downwardly into firing engagement with the primer 15. In such embodiment, the firing of the primerl 15 requires that the 'trigger mechanism'El be tripped by contact with the airplane. While this' L.-'. 7L construction is the, preferred embodiment, my 1n*- vention also contemplates as an alternatiyecon-` struction an arrangement in which a relatively high or predetermined impact force transmitted through the suspension. wire to the shell section ca n fire the primer: and detnate the. shell section without having to trip` the trigger mechanism Suchmodied embodiment is obtained by merely forming. the end ofy each slot |`|2-with aV gradual slope |1210, as shown in Figure 13, in-

stead. offwith a right angleshoulder. These slopihg rear. ends |1210 are. inclined at'anangle which' isfcalculated to let the sleeve extension IAE and plunger, 'l5 jump forwardly intoV firing engagementwith the primerunderthe action of inertiaz an. extremely. heavy impact shock is 'transmanner of rmg. the shell section by impact shock through the Wire might be employed advantageously when using a relatively short length of wire. The theory of operation would bethat becauseof the shortnessof thewire theshell section 4would necessarily he'v in close proximity to any airplane striking the wire, and hence the detonation of the shell section immediately upon the airplane striking the wire. would produce effective results. Some of this ring sensitivity to impact shock through the wire might be incorporated in constructions using. a long length of wire,` An airplane strikingvthe wire at an elevated point near the parachute will. not cause near as much impact shock at the shell section as will an airplanestrikingrthe wire at allow* point near the shell section The firing sensitivity may he proportioned so. that the relativelyv smallerimpat shocky at the shell section resultng.from the airplane striking the upper portion o'f the `wirewill no t i-lre,` the shell section, but the. greater impact shockH resulting from the airplane. striking the wire, in proximityyto the shell section. will detonate the latter. Thissensitive type, ofn firingl apparatus mightJ a'lsone adapted to a shra'pnel type of projectile where the shrapnel balls Awould be red from the openrear ofthe. frontv shell section 31a toward the airplane. For exan plein the. construction illustrated it would hepossible to makethe wall 5,9rather weak and to dispose same sharpnel balls on the inner, side of said. wallto bevblown upwardlywith the wall toward the airplane.

Figures 32 and 33 illustrate an optional feature which,may he incorporated in orY associated with' the third powder train ring |03 if desired. This' feature is that of beingA able to lconvert thel shell into a, timed high explosive shell, asprevously referred to in the description of said ring, Y When the ring |03 is Aconstructed tohave this convertible feature, it is formedwith twoangularly spaced grooves 2555` and 255 in. its frontfface; These grooves .are preferably .in diametrically1 Op-M posite relation, and may be flash vpassages o rfmay be packed with black powder o1; any othersuit-j able igniting material. Sucdmaterialfhasfnot. been shown to avoid obscuring the.. illustrations..

Figure 32 illustrates the 1vringri'n itsnorrnlal lposir oositoatfie groote 26.5.- comision tho. ti-xoo te.. 4.4. with. tho ootooaiot 51 for: roo 1 f ma the. ooraokloto ot #lo predotormooa alti; tude'jw this. position, th.` ther` groove. 26.6. Iioroly Standsidlo, the primos-15 remaining core nctedf with the. booster charge 12 tthrorig-lif pas. s'alg'esfll, L22., l,9',. 'L4 ion exploding-`the Shell Should thmfoorbfliroot. In this normal. Position off tho ri .a tho, lower. ond.. 'ofY the groote.v 265. registers with the. transfer port MN5 vvhihis f.l r `r ed. in the. stationary: spacing ring |02, `ancl thsoogowhioll Port theinitionottroin.

troosirrod 11o-tho: groove.- 2.5.5. The upper end. of, said Vgrooveis formed withl a roloifawfdlyl facing port 1.0%. whioh fogiotors.. at. With a port 6.8: opening ietothofdet.

een in. when rings 2. and 93A's this. time Y r nator. 6].. Theothrfer. groei/.e i? |.is,'E perrormingno functionin thisposition.,ofthegring` 113;` As 're viously described, the primer.l thirrible: llzhasa.. plurality of radially extending.ports, |24I', all on which canre in a forward-venting.directionbeyond the forward.edgeofthgring l|8when the thimble: is in. its forward. safetypsition, Whenth'ethimble .isin its v rearward firing; position, that` group ofy the. ports" |21. shown Ials-being lowerfmQst registers with a cooperating. series-oty stationary. ports |22 which extend. outwardly. through the ring II8 and sleeve 84 andopen ntotheright angle ports |09. As shown in Figure. 2r, these right angle ports IUSv areadaptedtorethrough passageways 14 which openf into. the. booster charge 12. Thus, in thenormal position of the; converting ring |02, thetimetrainds olperativetoA open the shell for ejecting. themarac'hute4 and theI primer l5. is operative. to. firethe; booster charge 12 andexplodethe shell. Also, it willbe noted that in this' positionofV the: a.;ip aratus.V the primer is capable of exploding thel shell. either upon direct percussion: of the; shell., against an airplanev before. ejectiony of` the.. parachute, or.. upon tripping of] the triggery mechanismA 5|. against an airplane .after ejection of. the. para-V chute.

Figure 33, illustrates.. the, transposed position of the grooves 2,65 andlli.l when thering |ll3,y has been turnedthroughQO in a clockwisefqirection to a position which.. converts the shell into a timed higheiplosiye projectile? Inthis position of the. ring, the. grooverz-,GS stands idler no`,corn. muvnicationI beingv established; from` they time train to lthe portl 6.8; anddetonator. 6J, and hence there is no timed ribrneniijigl of. the. shell= for.. the.A ejection of the parachutefandwire.: However1 the: other grooveT 255 now. o .ccupesan effective` positionfory establishing communication from the time train to the right anglel ports |09. and passageways 1.4. anstrengen. .the booste. charge' 12 for firing thehigh explosive charge- 43. T h'e` lower endof thegrogve 255 is..permanently` con-Q nected with oneroij more of 1the right angle ports. |09, and. when the rir1 g is in,this converting. por. sition thesev ports. register`r with cprrespon'ding p'assagewegrsl thea1,"lead..'toi the ,booster charge "l2,

The upper end of:A saidgroove is then in registration with the port lplin:thepstationayrng; |02, whereby. the time. train kresthrpughy thef; groove 26.6 for exploding the isholloftonthelapso of a set timeinterval.E 'Ilhvi'suioptional.featureeng` ablesthe shell tobeinstantly converted from the` parachute .'type -to ,the L co'rnvrentional`` timed high explosive type. This wgulldlenable'diiferent types ofY aotioirorof lire-to @carried on, Withootthe necessity of providing. the. v. gun fwithY moreythan,y one: type of projectile;V

Whoo' lthef hat is. thus.

e, con-erede ma.explose.omettere 

